2. Ratio and Scales have many uses such as maps,
building blue prints and even the model train
you may have in your home!
Eddau composed the works of "1919 Finnish Tietosanakirja ("Encyclopedia"). Scanned by Janke" and "Mike
Chapman" (https://commons.wikimedia.org/wiki/File:Train_scale_4-4-0.JPG), „Train scale 4-4-0“, marked as public
domain, more details on Wikimedia Commons: https://commons.wikimedia.org/wiki/Template:PD-self
3. Using Ratios and Scale
The ratio of staff to students at a school is 3:35. There are a total of 1,520 students
and staff at the school. How many students and how many staff are at the school?
Notice a total quantity is given. Use scale factor.
3𝑥 + 35𝑥 = 1520
38𝑥 = 1520
𝑥 = 40 scale factor
Now use the scale factor to determine the number of students and staff:
Staff = 3 x = 3 ( 40 ) = 120
Students = 35(x) = 34(40) = 1,400
4. Using Ratio and Scale
The ratio of a rectangle’s width to length is 2:3. The width is 10 inches. What
is the length?
Use proportions when the total is not given
𝑤𝑖𝑑𝑡ℎ
𝑙𝑒𝑛𝑔𝑡ℎ
Set up ratio
2
3
=
10
𝑥
Cross multiply
2𝑥 = 3 10 Solve
2𝑥 = 30
𝑥 = 15 Answer
The length of the rectangle is 15 inches